The present invention relates to a binder resin applicable to polyolefinic resins, for example, polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, etc. In more detail, it relates to a primer, paint, ink and adhesive composition to be used for the purpose of protection or beautiful ornament of polyolefinic resin moldings, films, etc.
Because of high productivity and broad degree of freedom for design as well as many advantages of light weight, antirust, shock resistance, etc., in recent years, plastics are used very frequently as the materials for automotive parts, electrical parts, building materials, food packaging film, etc. Above all, because of low price and many excellent properties such as moldability, chemical resistance, heat resistance, water resistance and good electrical characteristics, polyolefinic resins are used in broad range as industrial materials and are one of the materials that the growth of demand is most expected in future.
Different from synthetic resins with polarity such as polyurethane resin, polyamide resin, acrylic resin, polyester resin, etc., however, polyolefinic resin is nonpolar and crystalline, leading to drawbacks of difficult paintability and adhesion.
For the painting and adhesion onto such hard-adherent polyolefinic resin, low-chlorinated polyolefin that has strong adherence onto polyolefinic resin has been used so far as a binder resin.
For example, in Japanese Unexamined Patent Publication Nos. Sho 57-36128 and Sho 59-166534Japanese Patent Publication No. Sho 63-36624, etc., low-chlorinated polypropylene or low-chlorinated propylene-xcex1-olefin copolymer with chlorine content of 5 to 50%, containing carboxylic acid and/or carboxylic anhydride, is proposed as a painting primer or coating binder resin onto polyolefinic moldings.
Moreover, a composition (Japanese Unexamined Patent Publication Nos. Hei 4-248845 and 5-25405) having modified copolymer obtainable by graft copolymerizing xcex1, xcex2-unsaturated vinyl monomer containing hydroxyl group onto styrene.conjugated diene block copolymer, followed by further chlorination, as an essential component, a composition (Japanese Unexamined Patent Publication No. Hei 5-25405) having chlorinated product of graft modified product from styrene.isoprene block copolymer as an essential component, a composition (Japanese Unexamined Patent Publication Nos. Hei 5-112750 and Hei 5-112751) having chlorinated product of graft modified product from propylene-ethylene-xcex1-olefin random copolymer as an essential component, etc. are also proposed.
Although these compositions exhibit good adherence onto hard-adherent polyolefin, they are remarkably poor in the xe2x80x9cgasohol resistance testxe2x80x9d being a criterion of solvent resistance, that is, in a testing method wherein painted plate is soaked into a gasoline/alcohol mixed solution (gasohol) obtainable by adding 10% of lower alcohol such as methanol or ethanol to regular gasoline and whether the solvent resistance is good or bad is judged by a time until the painted film is peeled off.
Also, a method of crosslinking carboxyl group-containing chlorinated polyolefin with epoxy resin that can be seen in Japanese Patent Publication Nos. Sho 63-50381 and Hei 01-16414 and Japanese Unexamined Patent Publication No. Hei 8-100032, etc., is excellent in the socalled gasoline resistance to soak only in regular gasoline, but poor in the gasohol resistance property.
Further, such descriptions can be seen that a composition (Japanese Unexamined Patent Publication Nos. Hei 7-247381 and Hei 7-247382) having modified chlorinated polyolefin obtained by reacting carboxyl group-containing chlorinated polyolefin with low-molecular diol or low-molecular compound containing hydroxyl group and amino group as an essential component and a composition (Japanese Unexamined Patent Publication No. Hei 10-158447) obtained by mixing carboxyl group-containing chlorinated polyolefin with acrylic-modified chlorinated polyolefin that was modified with acrylic resin with glass transition point of higher than 60xc2x0 C., etc. are excellent in the gasohol resistance, but it is difficult to say that both really satisfy the gasohol resistance.
The invention provides a primer composition with improved gasohol resistance and adherence usable for painting the moldings, sheets, etc. of polyolefinic resins.
The primer composition of the invention that solves the subject aforementioned is a binder resin for polyolefinic resins comprising carboxyl group-containing chlorinated polyolefin obtainable by graft copolymerizing at least one kind of unsaturated carboxylic monomer selected from carboxylic acid and/or carboxylic anhydride onto polyolefin (I) in amounts of 1 to 10 wt. % and then chlorinating to chlorine content of 10 to 30 wt. %, and having carboxyl group-containing chlorinated polyolefin (II), which contains only not more than 2% of a component with molecular weight of 2,000 or lower, being the low-molecular weight region of said carboxyl group-containing chlorinated polyolefin, and which has a value of Mw/Mn, being a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), of not more than 4, as a major binder resin.
The polyolefin graft copolymerized with unsaturated carboxylic acid concerning the invention can be obtained by melting polyolefin under heat and, if need be, reducing viscosity or degrading it by thermal decomposition, and then by graft copolymerizing unsaturated carboxylic acid monomer of carboxylic acid and/or carboxylic anhydride in amounts of 1 to 10 wt. % batchwise or continuously in the presence of radical generator.
As the polyolefins (I), crystalline polypropylene, noncrystalline polypropylene, propylene-xcex1-olefin copolymer etc. can be used solely or by mixing two or more kinds, but, from the points of workability and adhesiveness of binder resin, a crystalline polypropylene with weight average molecular weight of 10,000 to 150,000, a propylene-xcex1-olefin copolymer with weight average molecular weight of 10,000 to 150,000 in which 70 to 97 mol % of propylene component is contained and number of carbon atoms is 2 or 4 to 6, a propylene-butene-ethylene terpolymer with weight average molecular weight of 10,000 to 150,000 in which 70 to 97 mol % of propylene component, 2 to 25 mol % of butene component and 2 to 25 mol % of ethylene component are contained, or the like can be used. In the case of propylene-xcex1-olefin copolymer, the xcex1-olefin unit is preferable to be at least one kind of xcex1-olefin with number of carbon atoms of 2 or 4 to 6 selected from, for example, ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 3-methyl-l-pentene and 1-hexene.
If the weight average molecular weight of raw material polyolefin (I) is under 10,000 or the propylene component is under 70 mol %, then the adherence to polyolefinic resin and the gasohol resistance become poor, and, if the weight average molecular weight exceeds 150,000, then the primer does not become fine particles when painting by air spray etc. to spoil the beautiful appearance of painted surface, which is unpreferable. Moreover, if the number of carbon atoms of xcex1-olefin of propylene-xcex1-olefin copolymer exceeds 6, then the adherence to polypropylene resin becomes poor. Furthermore, the propylene content of propylene-butene-ethylene copolymer being terpolymer is preferable to be 70 to 97 mol % as described above, the butene content is preferable to be 2 to 25 mol % and the ethylene content is preferable to be 2 to 25 mol %.
The unsaturated carboxylic acid monomers usable for introducing carboxyl group include acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, intaconic acid, itaconic anhydride, aconitic acid, aconitic anhydride, etc. and the amount of graft copolymerization is preferable to be 1 to 10 wt. % to polyolefin. If under 1%, the gasohol resistance becomes poor and the adherence to upper paint also becomes poor. If over 10%, the adherence to polyolefinic resin becomes poor and simultaneously increased solution viscosity due to hydrogen bond is seen, resulting in gelation on preservation and poor workability by air spray etc.
The radical generators to be used for the graft copolymerization reaction between polyolefin (I) and unsaturated carboxylic acid monomer include, for example, peroxides such as di-tert-butyl peroxide, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxide benzoate, methyl ethyl ketone peroxide and di-tert-butyl diperphthalate and azonitriles such as azobisisobutyronitrile.
The chlorine content of carboxyl group-containing chlorinated polyolefin (II) to be used in the invention is preferable to be 10 to 30 wt. %. If the chlorine content is under 10 wt. %, then the solubility into organic solvents such as toluene and xylene is poor and uniform solution cannot be obtained, resulting in gelation at low temperature or generation of grains, hence the solution becomes not to be applied as a primer. If the chlorine content exceeds 30 wt. %, the adherence to polyolefinic resin and the gasohol resistance become poor, which is unpreferable.
The less the component of low-molecular weight region of carboxyl group-containing chlorinated polyolefin (II) to be used in the invention, the better the gasohol resistance. That is, if the component with molecular weight of 2,000 or lower is contained over 2%, the gasohol resistance becomes poor remarkably. Moreover, the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) of (II), that is, the value of Mw/Mn is preferable to be not more than 4. When it exceeds 4 due to increase in the component of high-molecular weight region, the primer does not become fine particles when painting by air spray etc. and the beautiful appearance of coated surface is spoiled, which is unpreferable. When it exceeds 4 due to increase in the component of low-molecular weight region, the gasohol resistance becomes poor.
Besides, the content of low-molecular weight component with molecular weight of 2,000 or lower and the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), that is, Mw/Mn were determined by means of gel permeation chromatograph (GPC), using polystyrene with known molecular weight and narrow molecular weight distribution as a standard substance.
The carboxyl group-containing chlorinated polyolefin (II) to be used in the invention can be obtained by warming to completely dissolve polyolefin that was graft copolymerized with unsaturated carboxylic acid into solvents for chlorinating reaction, for example, chloroform, carbon tetrachloride, tetrachloroethylene, tetrachloroethane, etc., and then blowing-in chlorine gas to react at applied pressure or ambient pressure in the presence of radical generator as described above or under irradiation of ultraviolet rays, or in the absence of these radical generator and ultraviolet rays. The chlorinating reaction is conducted unusually at a temperature between 60xc2x0 C. and 120xc2x0 C.
As the method for removing low-molecular weight component of carboxyl group-containing chlorinated polyolefin, two methods of (1) a method for extracting to remove low-molecular weight component in carboxyl group-containing polyolefin before chlorination with solvent and (2) a method for extracting to remove low-molecular weight component in carboxyl group-containing chlorinated polyolefin after chlorination with solvent can be proposed.
For removing low-molecular weight component by the method (1), it is possible to remove by making carboxyl group-containing polyolefin before chlorination powdery, granular, pellet-like or molten state and by adding sole solvent selected from a group consisting of aliphatic hydrocarbon, aromatic hydrocarbon, alicyclic hydrocarbon, halogenated hydrocarbon, alcohols, esters, ketones and ethers with boiling point of lower than 120xc2x0 C. or a mixed solvent thereof to dissolve out the low-molecular weight component into these solvents within a temperature range of 10 to 100xc2x0 C.
The reason why the boiling point of solvent was made to be lower than 120xc2x0 C. is because of that, if the boiling point is too high, solvent becomes to be liable to remain in the carboxyl group-containing polyolefin or carboxyl group-containing chlorinated polyolefin (II), resulting in chlorination of said solvent or decreased physical properties of primer, which is unpreferable.
The reason why the temperature on extraction was made 10 to 100xc2x0 C. is because of that, if under 10xc2x0 C., removal of low-molecular weight component by extraction becomes incomplete, which is unpreferable. Also, if over 100xc2x0 C., even high-molecular weight component is removed to decrease the recovery rate, which is unpreferable. When using a solvent with boiling point of under 100xc2x0 C., it is preferable to conduct the solvent extraction in a completely closed-up pressure vessel.
The method for removing low-molecular weight component by the method (2) is also possible to conduct with carboxyl group-containing chlorinated polyolefin, following the method (1). When the carboxyl group-containing chlorinated polyolefin is in solution, the temperature on extraction is preferable to be as low as possible, but, if under 0xc2x0 C., the solvent extraction of low-molecular weight component cannot be conducted efficiently, because of too high viscosity. If the temperature becomes higher than room temperature, then the carboxyl group-containing chlorinated polyolefin dissolves into extracting solvent in large quantity to decrease the recovery rate, which is unpreferable. When the carboxyl group-containing chlorinated polyolefin is solid article, the higher the extraction temperature, the better, but, if over 100xc2x0 C., dehydrochloric acid etc. are caused to bring to instability, which is unpreferable.
As typical solvents with boiling point of under 120xc2x0 C. for removing low-molecular weight component, in the case of aliphatic hydrocarbon, pentane, 2-methylpentane, hexane, 2,2-dimethylbutane, 2,3-dimethyl-butane, heptane, 2-methylhexane, 3-methylhexane, 2,4-dimethylpentane, petroleum ether, petroleum benzine, etc. can be exemplified. In the case of aromatic hydrocarbon, benzene, toluene, etc. can be exemplified. In the case of alicyclic hydrocarbon, cyclopentane, methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, etc. can be exemplified. In the case of halogenated hydrocarbon, trichloromethane, tetrachloromethane, 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2-trichloroethane, 1,1-dichloroethylene, 1,2-dichloroethylene, trichloroethylene, etc. can be exemplified. In the case of alcohols, methanol, ethanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol, 2-pentanol, 3-pentanol, etc. can be exemplified. In the case of esters, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, isobutyl acetate, secbutyl acetate, etc. can be exemplified. In the case of ketones, acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, methyl isobutyl ketone, etc. can be exemplified. In the case of ethers, diethyl ether, dipropyl ether, diisopropyl ether, etc. can be exemplified.
The carboxyl group-containing chlorinated polyolefin (II) to be used in the invention can be used as it is by coating or spray painting in the state of clear varnish. But, it can also be used as a primer, paint and ink for polyolefinic resin moldings and films by adding titanium dioxide, carbon black, aluminum paste, coloring pigment, etc. and, if need be, other additives, for example, ultraviolet absorber, antioxidant, pigment sedimentation preventer, etc. followed by kneading. Moreover, it can also be used as an adhesive for those substrates.
Moreover, the carboxyl group-containing chlorinated polyolefin (II) exhibits balanced physical properties of painted film by itself, but, by adding alkyd resin, acrylic resin, polyacrylic polyol, polyester resin, polyesterpolyol, polyether resin, polyetherpolyol or polyurethane resin for use, more characteristic binder resin composition can be obtained.
The addition of said resins is very useful, since the adherence onto upper coating paint and the weather resistance that was a drawback of chlorinated polyolefinic resin improve. From such reason, by allowing to have a resin mixed at a ratio by weight of carboxyl group-containing chlorinated polyolefin (II)/said resin group=3/7 to 9/1 as a major binder resin, more improved binder resin composition can be obtained.
Namely, contrary to the facts that, when said resin group is mixed with conventional carboxyl group-containing chlorinated polyolefin, not only the adherence onto polyolefin decreases, but also the gasohol resistance decreases remarkably, in the case of the carboxyl group-containing chlorinated polyolefin (II) of the invention, mixing of said resin group even up to 70% at maximum does not injure the adherence and the gasohol resistance. Furthermore, when titanium dioxide, carbon black, coloring pigment, etc. are kneaded beforehand with said resin and then (II) is mixed, there is an advantage that stabilized pigment dispersion can be achieved. That is, minimum requirement level of said resin to achieve stabilized pigment dispersion is 10%.
For the chlorinated resin like the carboxyl group-containing chlorinated polyolefin.(II) obtainable by the method aforementioned, epoxy compound has been added so far as a stabilizer for use. Although the epoxy compound is not particularly restricted, one compatible with chlorinated resin is preferable, and such epoxy compound with epoxy equivalent of around 100 to 500 and with one or more epoxy group per molecule can be exemplified.
For example, epoxidated soybean oil and epoxidated linseed oil obtainable by epoxidating vegetable oils having natural unsaturated group with peracids such as peracetic acid, epoxidated fatty acid esters obtainable by epoxidating unsaturated fatty acids such as oleic acid, tall oil fatty acid and soybean oil fatty acid, epoxidated alicyclic compounds represented by epoxidated tetrahydrophthalate, and products obtainable by condensing bisphenol A or polyhydric alcohol with epichlorohydrin, for example, bisphenol A glycidyl ether, ethylene glycol glycidyl ether, propylene glycol glycidyl ether, glycerol polyglycidyl ether, sorbitol polyglycidyl ether, etc. are exemplified. Moreover, monoepoxy compounds represented by butyl glycidyl ether, 2-ethyl-hexyl glycidyl ether, decyl glycidyl ether, stearyl glycidyl ether, allyl glycidyl ether, phenyl glycidyl ether, sec-butylphenyl glycidyl ether, tert-butylphenyl glycidyl ether, phenol polyethylene oxide glycidyl ether, etc. are exemplified. Moreover, metallic soaps such as calcium stearate and lead stearate, organometallic compounds such as dibutyl tin dilaurate and dibutyl tin maleate and hydrotalcite compounds, which are used as the stabilizers of poly (vinyl chloride) resin, can also be used, and it doesn""t matter whether these are used in combination.
The carboxyl group-containing chlorinated polyolefin (II) obtainable by the method aforementioned can be used by replacing the solvent to aromatic hydrocarbon such as toluene or xylene, or alicyclic hydrocarbon such as cyclohexane or methylcyclohexane, being good solvents, after completion of chlorinating reaction and after distillation of chlorination solvent, and then by adding stabilizer such as epoxy compound. In the case of the carboxyl group-containing chlorinated polyolefin (II) of the invention, however, due to the hydrogen bond originating from carboxyl group contained, the solution viscosity increases over time. For preventing this, it is possible to partially add a solvent with polarity, for example, ester type solvent such as ethyl acetate, ketone type solvent such as methyl ethyl ketone, ether type solvent such as tetrahydrofuran, or alcohol type solvent such as isopropanol for use. Above all, the effect of alcohol type solvent is conspicuous and it is only necessary to add 1 to 10 wt. % to the solvent composition.
Moreover, it may also be safe that, after completion of chlorinating reaction and after removal of hydrochloric acid in the solvent for chlorinating reaction such as chloroform, epoxy compound or the like is added as a stabilizer and the stabilized material is solidified by supplying to a vent extruder equipped with solvent-removing suction at the part of screw shaft, and, thereafter, it is dissolved into solvent such as toluene. The solidification can be implemented by the publicly known method, for example, by using a vent extruder equipped with underwater cutting pelletizer at the outlet part of extruder, a pelletizer capable of cutting strand-like resin, and the like.
The feature of the invention lies in the carboxyl group-containing chlorinated polyolefin (II) with low-molecular weight component of carboxyl group-containing chlorinated polyolefin removed and with moderate ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), that is, Mw/Mn value, thus providing a primer composition that exhibits excellent adherence and gasohol resistance to polyolefinic resins. Although it is not clear why the removal of low-molecular weight component improves the gasohol resistance, it is considered that these low-molecular weight components are addition products of chlorine and carboxylic acid to olefin oligomers produced through the decomposition of polyolefin by heat and catalyst. If considering that the swelling or dissolution of this component into gasoline and alcohol being components of gasohol lowers the gasohol resistance, it can be said that the removal of low-molecular weight component is one of the reasons that improves the gasohol resistance.